In response to tighter guidelines recently imposed by environmental and regulatory agencies, the control of pollution, silt and sediment found in storm water runoff and other sources of water is receiving ever-increasing attention at all levels of federal, state, and local government. Federal and state agencies have issued mandates and developed guidelines regarding the prevention of non-point source (storm water caused) pollution that require action by governmental entities. These mandates affect the management of water runoff from sources such as storms, slopes, and construction sites, in addition, there are many other laws and regulations in place that restrict the movement or disposal of significant amounts of water. Such laws and regulations have a significant impact on, for example, the ways that states, municipalities, highway authorities and other responsible bodies can drain or otherwise dispose of storm runoff or other water falling on or passing over highways, roadways, parking lots and the like.
Bioretention swales, also known as grassy swales grassy drainage vegetated swales, bioretention swales, or simply “swales,” are a common and well known way of filtering, treating and/or draining storm runoff or other dirty water that falls on and/or passes over highways, roadways, parking lots and the like. Swales function as soil and vegetation-based filtration systems, removing pollutants through a variety of physical, biological, and chemical treatment processes. The interaction of fluid with vegetation in the swale promotes a more even distribution of the fluid and retention of sediments. Such swales are routinely designed as one or more parts of an overall drainage infrastructure for storm water runoff, along with other less aesthetically pleasing elements, such as gutters, dams, sewers, aqueducts and the like. Unlike many of these other structures, however, grassy swales are preferred for their more pleasing appearance and their ability to provide a natural means for filtering and otherwise treating passing storm water or fluid runoff.
In a typical application, a swale is specifically sized to handle the estimated amount of runoff from an adjacent land improvement for a given time period, for example, ten years. At that time, the party responsible for the swale, such as a municipality highway authority, developer or property owner, will typically conduct a reconstructive overhaul or replanting of the grass layer in the swale, as it is only a matter of time before pollutants and contaminants overrun the grass and topsoil layers of the swale. Frequently, such an overhaul or reconstruction may be needed ahead of schedule, due to the generally incessant flow of chemicals and pollutants from roadways and similar structures that are washed into swales and drainage systems by storms and other runoff events. Such overhauls or reconstructions are costly and time consuming, and additional problems may ensue in the event that they are delayed or needed ahead of schedule. For example, a weak or failing swale may undesirably pass an inordinate amount of pollutants, sedimentation and other debris onward into a subsequent drainage system during the time that it takes to overhaul or replant the swale. In addition, as regulations tighten or various applications require a higher standard of filtration or pollutant removal, many typical swales and other current methods and systems for removing pollutants normally found in storm water runoff, including hydrocarbons, nitrates, and phosphates, may prove to be inadequate.
Although a swale may offer removal of ultra-fine and dissolved and dissolved constituents, gross pollutants such as coarse sediment, trash and debris can reduce system efficiency and increase maintenance needs. During periods of high storm water flow, swales may have limited capacity to process large quantities of fluid. Swales may not be able to process all of the storm water, for example, during heavy rain hill events. Backups that result in localized flooding of the surrounding areas may occur as a result. In some instances, swales may be used with an underground drainage basin system to catch high storm water flows. The drainage basin systems can catch overflow and release the excess fluid flow into underground drain and piping systems. Trash and debris, however, may also accumulate and be released into the drain and piping systems, along with the overflow storm water.
Accordingly, there exists a need for more effective methods and apparatuses for filtering and treating polluted or dirty water, such as storm water runoff, falling on or passing over highways, roadways, parking lots and the like. In particular, there exists a need for alleviating the work load carried by some grassy swales that allows for capture of floatables, trash, and other debris.